Crank structure for treadmills

ABSTRACT

An improved crank structure for treadmills, each of the treadmills has two pedals for a user to step, the pedals respectively connect on one of their ends with the periphery of a rotary wheel, and are linked with cranks respectively on the front and the rear sides of the rotary wheel, the cranks are connected on their internal end portions with the center of the rotary wheel, the cranks are provided each with a first section which has an included angle with the vertical diametric line of the rotary wheel, at the tailing end of the first section, there is a bent section for connecting with the center of the rotary wheel. A user using such a treadmill needs only to exert a small force at the uppermost position of the rotary wheel for stepping; this can prevent probable damage of exercising.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention is related to an improved crank structurefor treadmills, and especially to such a structure of which the crankscan allow people to step pedals more conveniently with smaller forcewhen they get to the top point within a circular motion.

[0003] 2. Description of the Prior Art

[0004] People nowadays live busily and the spaces they live are more andmore smaller; it is quite difficult to keep appropriate amount ofexercising. In view of this situation, there have been various indoorsporting instruments in the markets, such sporting instruments can beused in a limited space without influence by time and weather;therefore, they are very suitable as sporting instruments for health formodern people.

[0005] Treadmills are of one kind of popularized indoor sportinginstruments, basically, they are provided each with two pedals forpeople to step with their feet, when the feet act in running or steppingmode thereon, the pedals is moved up and down alternately; in this way,a function of exercising simulating running or jogging outdoors can beobtained.

[0006] The basic principles for such treadmills are expressed as shownin FIG. 1, wherein, a treadmill of such is provided with a first pedal10 and a second pedal 20, the left foot “L” of a user can step on thefirst pedal 10, while the right foot “R” can step on the second pedal20. The pedals 10, 20 respectively connect on their front ends with afirst crank 11 and a second crank 22 mutually oppositely directing. Thecranks 11, 22 respectively connect on their external end portions in themode of linking with peripheral points 13, 24 on a rotary wheel 30. Insuch a crank mechanism of the treadmill, when the user runs or steps atthe fixed position, the cranks 11, 22 will respectively run circularmotions about the center “O” of the rotary wheel 30. This makes the endsof the pedals 10, 20 move up and down successively to give the desiredfunction of exercising.

[0007] Referring to FIGS. 1-3, by virtue that the cranks 11, 22 arestraight and are given with predetermined lengths to connect each fromthe peripheral points 13, 24 on the rotary wheel 30 to the center “O” ofthe rotary wheel 30, the lengths for motion thereof are bothapproximately equal to the radius “r” of the rotary wheel 30. Forexample, when the first pedal 10 is at the uppermost position (deadpoint) as shown in FIGS. 1 and 2, this is the position which exhaustforce the most, here the action force completely vertically gets throughthe center “O” of the rotary wheel 30 with an arm of force of merelyzero, the required torque will not be created. This is why the stage forthe first pedal 10 to move from the uppermost position 13 to aneighboring peripheral position 13 a is most difficult.

[0008] The source of power for running the rotary wheel 30 of such atreadmill is mainly the down pressing weight “W” of the user plus ahorizontal pushing force “P”. For example, as shown in FIG. 1, when theuser moves the crank 11 to the uppermost position 13 of the rotary wheel30, the force that the weight “W” of the user applying to this positionis ½ W assuming that the weight is averagely loaded; the forcecompletely vertically gets through the center “O” of the rotary wheel30, it does not have any tangential component to drive the rotary wheel30 to rotate. The main driving force at this time is the horizontalaction force “P” of the user. Assuming in an exercising case, thehorizontal component “f” (the vertical component “g” is functionless) ofthe half weight “W/2” through one leg of the user is extremely small,when the first crank 11 or the second crank 22 is rotated to theaforesaid uppermost position 13 or an area nearby the position, the usermust exert very hardly a horizontal action force “P” for further moving.

[0009] The rotating mechanism as shown in FIG. 4 is frequently seen onthe instruments such as a bicycle, the main chain wheel 35 thereof isprovided on the two sides thereof with a left pedal 15, a right pedal 25and cranks 17, 27; both the pedals 15, 25 are movable. In the drawingshown, when the right pedal 25 is moved to the uppermost position 13, aninclining stepping force P′ is exerted onto the main chain wheel 35 toprevent the above stated exhaustion situation at the uppermost position.However, as shown in FIG. 5, both the pedals 11, 22 of such aconventional treadmill are fixed, this forms a limitation, when thefirst pedal 11 has its end located at the uppermost position, the thighsand shins of the legs 181 of the user 18 must bend about the knee 182 asan axis to give a horizontal action force “P”. This not only makes anextreme large burden against physical strength of the user inexercising, but also repeatedly gives sudden adding of loading on theknee 182 during exercising. Inadvertent damage of sporting thereby maybe induced.

SUMMARY OF THE INVENTION

[0010] The present invention provides an improved crank structure for atreadmill, whereby, when the pedals and the linked ends of the cranksare moved to the uppermost position of the rotary wheel, a pushing forcecan be easily formed, this can prevent inadvertent damage of sporting.

[0011] To get the above stated object, the present invention mainlymakes the cranks thereof bent, the first section of each of them is setto form a angle with the vertical diametric line of a rotary wheel; atthe tailing end of the first section, there is a bent section forconnecting with the center of the rotary wheel. With this, the incliningcomponent of the weight “W” along the first section times the arm offorce, namely, the distance from the center line of the first section tothe center of the rotary wheel, to form a torque to push the crank awayfrom the uppermost position of the rotary wheel.

[0012] The present invention will be apparent in its novelty andfeatures after reading the detailed description of the preferredembodiment thereof in reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a schematic view showing the crank mechanism of aconventional treadmill and its motion in operation;

[0014]FIG. 2 is a schematic view showing the mechanism on one side andits motion in operation of the treadmill as shown in FIG. 1;

[0015]FIG. 3 is a schematic view showing the forces exerting for thetreadmill as shown in FIG. 1 and 2;

[0016]FIG. 4 is a schematic view showing the related mechanisms of theconventional chain wheel and pedals of a bicycle and their motions inoperation;

[0017]FIG. 5 is a schematic view showing a man steps on the conventionaltreadmill as shown in FIG. 1;

[0018]FIG. 6 is a schematic view showing the mechanism and its motionsin operation of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019] Referring to FIG. 6, the present invention likewise has twopedals 100, 200 for stepping respectively of the left foot “L” and theright foot “R” of a user, the pedals 100, 200 respectively have one oftheir ends connected to the two sides of a rotary wheel 300 with a setdiameter. The connecting ends of the pedals 100, 200 are respectivelyconnected with one of the ends of each of two cranks 110, 220, the otherof the ends of each of the two cranks 110, 220 are both connected withthe center of the rotary wheel 300.

[0020] The present invention is characterized by that: the length ofeach of the cranks 110, 220 measuring vertically on the rotary wheel 300equals to the radius “r” of the rotary wheel 300, and each of the cranks110, 220 can be bent for a suitable angle. In the embodiment of thecrank 110 shown in the drawing as an example, a first section 110 a ofthe crank 110 connecting movably to the pedal 100 makes an includedangle θ with a vertical diametric line Cv of the rotary wheel 300, thetailing end of the first section 110 a is bent to form a bent section110 b which connects with the center of the rotary wheel 300.

[0021] Such an improved design of crank will make generation of aninclining component “b” and another inclining component “c”perpendicular to the former component of a half of the weight “W/2”assuming the force provided by the user is the half of the weight “W/2”.For example, with the bending angle of the crank 110 shown in thedrawing, the distance between the centerline of the first section 110 aand the center “O” of the rotary wheel 300 is “d”, the incliningcomponent “b” will get a torque b×d.

[0022] Assuming an angle θ between the first section 110 a and thevertical diametric line Cv of the rotary wheel 300 is 45 degrees, theweight of the user is “W”, the abovementioned torque should be:

∵b=cos45°×W/2=25(kg)

∴the torque M=25×d(the set length)=25d(kg-cm)

[0023] Thereby, the torque produced when the user stands on the pedal100 or 200 is decided by the angle θ between the first section 110 a andthe vertical diametric line Cv of the rotary wheel 300 as well as thedistance “d” between the centerline of the first section 110 a and thecenter “O” of the rotary wheel 300. By setting of the values θ and “d”for the torque produced by the weight of the user at the uppermostposition of the rotary wheel, θ can be within 90 degrees, and aresuitably within 30° to 60° and is most preferably 45° as shown in thedrawing. And the first section 110 a is orthogonal to the bent section110 b (when the included angle between the two is 90°, the longest armof force can be obtained).

[0024] With the above stated improved design of the cranks 110, 220,when the crank 110 or 220 arrives at the uppermost position of therotary wheel 300, the torque produced by the weight “W” of the user willrender the rotary wheel 300 very easy to rotate away from the uppermostposition to a neighboring area thereof. In stepping, only an extremesmall horizontal action force “P” is needed from the user to make therotary wheel 300 get away from the uppermost position to go on rotate.The user needs only to exert a small force at the uppermost position forstepping; this can prevent probable damage of exercising with such atreadmill.

[0025] The embodiment cited above is only for illustrating a preferredembodiment of the present invention. It will be apparent to thoseskilled in this art that various modifications or changes can be made tothe elements of the present invention without departing from the spiritand scope of this invention. Accordingly, all such modifications andchanges also fall within the scope of the appended claims and areintended to form part of this invention.

1. An improved crank structure for treadmills, each of said treadmillshas two pedals for a user to step, said pedals respectively connect onone of their ends with the periphery of a rotary wheel, and are linkedwith cranks respectively on the front and the rear sides of said rotarywheel, said cranks are connected on their internal end portions with thecenter of said rotary wheel, said crank structure is characterized bythat: said cranks are provided each with a first section which has anincluded angle with the vertical diametric line of said rotary wheel, atthe tailing end of said first section, there is a bent section forconnecting with the center of said rotary wheel.
 2. An improved crankstructure for treadmills as claimed in claim 1, wherein, said firstsections of said cranks each has an included angle of within 90° withsaid vertical diametric line of said rotary wheel.
 3. An improved crankstructure for treadmills as claimed in claim 1, wherein, said firstsections of said cranks each is perpendicular to the corresponding oneof said bent sections.